Commit 8b3405e3 authored Apr 03, 2017 by Suzuki K Poulose Committed by Christoffer Dall Apr 04, 2017

kvm: arm/arm64: Fix locking for kvm_free_stage2_pgd



In kvm_free_stage2_pgd() we don't hold the kvm->mmu_lock while calling
unmap_stage2_range() on the entire memory range for the guest. This could
cause problems with other callers (e.g, munmap on a memslot) trying to
unmap a range. And since we have to unmap the entire Guest memory range
holding a spinlock, make sure we yield the lock if necessary, after we
unmap each PUD range.

Fixes: commit d5d8184d ("KVM: ARM: Memory virtualization setup")
Cc: stable@vger.kernel.org # v3.10+
Cc: Paolo Bonzini <pbonzin@redhat.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Christoffer Dall <christoffer.dall@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
[ Avoid vCPU starvation and lockup detector warnings ]
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Christoffer Dall <cdall@linaro.org>

parent 72f31048

arch/arm/kvm/mmu.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -292,11 +292,18 @@ static void unmap_stage2_range(struct kvm *kvm, phys_addr_t start, u64 size)
		phys_addr_t addr = start, end = start + size;
		phys_addr_t next;

		assert_spin_locked(&kvm->mmu_lock);
		pgd = kvm->arch.pgd + stage2_pgd_index(addr);
		do {
		next = stage2_pgd_addr_end(addr, end);
		if (!stage2_pgd_none(*pgd))
		unmap_stage2_puds(kvm, pgd, addr, next);
		/*
		* If the range is too large, release the kvm->mmu_lock
		* to prevent starvation and lockup detector warnings.
		*/
		if (next != end)
		cond_resched_lock(&kvm->mmu_lock);
		} while (pgd++, addr = next, addr != end);
		}

		@@ -831,7 +838,10 @@ void kvm_free_stage2_pgd(struct kvm *kvm)
		if (kvm->arch.pgd == NULL)
		return;

		spin_lock(&kvm->mmu_lock);
		unmap_stage2_range(kvm, 0, KVM_PHYS_SIZE);
		spin_unlock(&kvm->mmu_lock);

		/* Free the HW pgd, one page at a time */
		free_pages_exact(kvm->arch.pgd, S2_PGD_SIZE);
		kvm->arch.pgd = NULL;

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